Hi there, I'm currently in the process of getting my unRAID server setup and I have my user shares set to high-water as well as "automatically split any directory as required". I started the server with a 10TB drive, and after I transferred files off other drives, I added them to the array. I currently have a 10TB, 1TB, and 2TB drive in the array and so far, data is only being added to the 10TB drive, which is currently at 8.5TB full, with nothing added yet to the other drives.
It's my understanding that once the 10TB drive hit 5TB full it would start moving files to the other two drives until they're half full, before going back to the 10TB drive.